Energy Saver Power Factor Controller for Synchronous Motors

A technique for maintaining a synchronous motor at unity power factor (or minimum line current) from no-load to full-load conditions, assuring peak efficiency, is described. This concept stems from an adaptation of the Energy Saver Power Factor Controller for induction motors recently developed and patented by NASA Marshall Space Flight Center. The method constantly and automatically adjusts the dc field current of a 3-phase synchronous machine such that the ac line current will always be operating at the minimal point of the well known "V" curves. This is accomplished as the load varies over its full operating range.